https://learningnetwork.cisco.com/message/279101#279101
on that link you can download a packet capture that i attached...
i've read recently some conflicting ideas about the tagging of control traffic when vlan 1 is not present... my original thought sided with marko that l2 control traffic belonged to the switch.. here is marko's post:
http://blog.ipexpert.com/2011/01/19/old-ccie-myths-vlan-1/
he explores this idea at length, but this idea is incorrect...
this idea is refuted here:
http://www.fragmentationneeded.net/2011/01/revisiting-vlan-1-myth-again.html
and from the horse's mouth here:
(from Cisco Lan Switching Fundamentals)
naturally, i wanted to do my own testing, but my caps never showed tagging... i was using a dhcp windows client for monitoring and in the back of my mind my thought was that i'd never see dot1q tags because my windows nic simply didn't support tagging, therefore wouldn't show in the cap... well, breaking my current working topology was an annoying idea simply to prove that so i moved on with what i was currently working at the time...
this morning, of course, it was nagging me so i had to be sure... turns out that is correct... dot1q tags don't show up in my windows box caps, but they do with the linux caps...
note on dsw1 in the below output that vlan 1 is not included in trunking...
dsw1#sh int trunk
Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 200
Po2 on 802.1q trunking 200
Port Vlans allowed on trunk
Po1 10,20,200
Po2 10,20,200
Port Vlans allowed and active in management domain
Po1 10,20,200
Po2 10,20,200
Port Vlans in spanning tree forwarding state and not pruned
Po1 10,20,200
Po2 10,20,200
Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 200
Po2 on 802.1q trunking 200
Port Vlans allowed on trunk
Po1 10,20,200
Po2 10,20,200
Port Vlans allowed and active in management domain
Po1 10,20,200
Po2 10,20,200
Port Vlans in spanning tree forwarding state and not pruned
Po1 10,20,200
Po2 10,20,200
in the cap below note that the control traffic is tagged with vlan 1...
in fact all of the control traffic in the cap is tagged 1... but see for yourself, download the cap from the link and draw your own conclusions... also note that the cap is from the tshoot topology, which means that all supported protocols are represented as they would appear in cisco's topology... naturally it is my representation of that topology; it is not gospel...
have fun...
note about topology: vlan's 4 and 8 support the gns3 environment onto the switched network... so don't let those qinq's confuse you...
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